U.S. and Canadian jets intercepted eight Russian military aircraft as they neared American and Canadian airspace in two separate incidents, officials confirmed Saturday.

In both incidents the Russian aircraft never penetrated U.S. or Canadian airspace and appeared non-threatening, military officials said.

"They just continued on with their mission," said Army Lt Col. Michael Jazdyk, a spokesman for NORAD, the North American Aerospace Defense Command. "We were monitoring the situation to make sure they weren't going to go in our airspace."

On Wednesday at about 7 p.m. Pacific time two Alaska-based F-22 fighters were sent to identify six Russian military flying off the coast of Alaska. The Russian aircraft included two MiG-31 fighters, two long range bombers and two refueling tankers.

The aircraft turned south and headed back toward Russia.

Hours later, two Russian long range bombers were intercepted and identified by two Canadian CF-18 fighters off the coast of Canada.

"We suspect it was nothing more than a training exercise," Jazdyk said.

Sovereign airspace extends about 12 miles off the coastline, but an identification zone extends out 200 miles, allowing nations to identify aircraft before they become a threat.

Officials say such intercepts are not unusual. They occur on average nearly once a month, according to NORAD.